This invention relates to machinery for fabricating concrete pipe and, more particularly, to machinery for varying the temperature and pressure as is required for fabricating a pipe composed of a sulfur cement and aggregate.
Concrete composed of Portland cement is widely used in the construction industry. Such concrete has been utilized both for flat objects, such as walls and floors, as well as more complex objects, such as pipes. While such concrete has provided good service over long periods of time in many environments, problems have arisen in the use of such concrete in corrosive atmospheres as well as in the desert.
Recently, another form of concrete employing a sulfur cement in lieu of the Portland cement has shown great promise in resisting corrosion and in withstanding the environment of a desert.
However, problems have arisen in the fabrication of objects, be they blocks or pipes, fabricated from the sulfur concrete due to unknown long term effects of various manufacturing processes employed. In particular, by way of contrast with Portland cement which is mixed with a sand aggregate and water, the sulfur cement may be either in liquid or solid form at the time of the mixing with the aggregate. Other considerations arise in the preparation of sulfur concrete. No water is used in sulfur concrete. In addition, the sulfur concrete is a poor conductor of heat. Further, the sulfur cement must be liquified by heating during some part of the fabrication process, either before mixing or subsequent to the mixing with the aggregate.
The complexity of the manufacturing process is increased with the manufacture of sulfur concrete pipes and tubing in that centrifuging generally is used to provide a desired round cylindrical surface. To avoid stresses built up in the sulfur concrete material during the curing and cooling of the pipe, it is desirable for the pipe manufacturing machinery to be capable of providing the correct amount of heat, and for maintaining the rate of heat delivery at the requisite amount for insuring that all portions, both near the surface and deep within the sulfur concrete materials, be heated to the desired temperature and be permitted to cool at the desired rate.
Heretofore, pipe manufacturing machinery has not had the capability for satisfactorily performing all of the foregoing heat control functions while centrifuging sulfur concrete material. Furthermore as experience develops in the utilization and manufacture of sulfur concrete pipe, further variations in temperature and pressure profiles during the manufacturing process may become necessary. Present day equipment does not have the capacity for providing such variation in temperature and pressure required for optimizing strength and corrosion resistance of the sulfur concrete pipe.